Recently, with miniaturization, reduction in weight and sophistication of electronic devices, refinement and density increase of copper wiring have been strongly desired for printed-wiring boards.
A semi-additive process is one of production methods for forming a micro wiring. According to this method for forming a wiring, a metal layer called a seed layer is formed on an insulation layer, a plating resist layer is formed on the surface thereof, and after that, exposure and development are performed to form a resist pattern. After that, an electrolytic copper plating is provided to an opening, the resist is stripped, and the seed layer is removed by etching to form a copper wiring.
Conventionally, the surface of the insulation layer is subjected to the roughening treatment to form concavity and convexity chemically or physically, and the adhesion between the insulation layer and the chemical copper plating as the seed layer is ensured by the physical (anchor) effect. The thickness of the chemical copper plating is generally 0.5 to 1 μm or less. Therefore, since the surface of the chemical copper plating is formed in conformity to concavity and convexity of the insulation layer, regarding the surface roughness, the arithmetic average roughness Ra is large (0.4 to 1 μm). Recently, the width of copper wiring has been decreased to 10 μm, and moreover, decrease to several μm has been studied for next-generation products. However, the surface of the conventional chemical copper plating that is formed on the insulation layer coarsely roughened is markedly uneven, and therefore, in the exposure process for a dry film resist, it is difficult to form a fine pattern with a wiring width of less than 10 μm because of reduction in the resolution due to light scattering.
Recently, for micro wiring, an insulation layer material, which has a surface roughened at a level lower than conventional insulation layer materials and can ensure adhesion to the chemical copper plating, has been produced. The insulation layer material ensures adhesion to the chemical copper plating with the physical effect and chemical effect of low-level roughening. The surface of the insulation layer to which the chemical copper plating is applied is almost flat and smooth without concavity and convexity. In the case of the surface of chemical copper plating, adhesion to a dry film resist material is insufficient, and it is impossible to form a pattern.
Further, for the production of micro wiring, there is a case where a copper film formed by the sputtering method (sputtered copper) is formed on the seed layer instead of the chemical copper plating (thickness of sputtered copper: 0.5 to 0.7 μm). The surface of the sputtered copper is flatter and smoother than the chemical copper plating, and it is impossible to obtain sufficient adhesion to a dry film resist material, and therefore, it is difficult to form a pattern.
As conventional roughening agents for copper, for example, a surface treatment agent containing hydrogen peroxide, mineral acid, azoles, silver ion and halogen ion (Patent Document 1), an etching solution containing oxoacid, peroxide, azoles and halide (Patent Document 2), a surface roughening treatment solution containing hydrogen peroxide, sulfuric acid, benzotriazols and chloride ion (Patent Document 3), a micro-etching agent containing sulfuric acid, peroxide, tetrazole and a metal ion having a potential nobler than that of copper (Patent Document 4), and a surface roughening agent containing sulfuric acid, hydrogen peroxide, aminotetrazole, a tetrazole compound other than aminotetrazole and a phosphonic acid-based chelating agent (Patent Document 5) are disclosed.
In a semi-additive process, a resist pattern is formed, an electrolytic copper plating is provided to an opening thereof, and at the time of the resist stripping step, when the width of a resist pattern is smaller than 10 μm, the resist does not sufficiently swell with a conventional resist stripping liquid or the like containing sodium hydroxide that allows the dry film resist to swell and to be stripped, because the space of the adjacent resist pattern is narrow. For this reason, stripping is insufficient. Further, dry film resist materials for micro wiring formation have been improved to be a low-swelling type having a high resolution, and therefore, such resists cannot be stripped with conventional stripping liquids.
As resist stripping liquids containing an organic compound, a stripping agent made of an aqueous solution containing quaternary ammonium hydroxide, water-soluble amine and hydroxylamines (Patent Document 6), a stripping agent made of an aqueous solution containing ammonium fluoride, a polar organic solvent and epoxy polyamide (Patent Document 7), a resist stripping liquid containing alkanolamine, diethylhydroxylamine, diethylene glycol monoalkyl ether, sugars and water (Patent Document 8) and the like are disclosed.